The "to burn" probably means to gamble $3 of TRX or BTC and mine. He expects he'll lose all of it in exchange of BFG tokens but he wants to know which one has a cheaper mining price.

I tried to convert the current mining rate for in-house game for BTC and Tron using the rate on Coingecko and it appeared BTC is a bit higher.
- BTC 0.00008899 @ $36,182.87 = 3.22
- TRX 45.8711340 @ $0.069382 = 3.18


Just correct me if I'm wrong Nurbag but if that is what you're asking then the difference isn't that much. You have to remember also that the odds of winning or losing doesn't depend on what cryptocurrency you use.

Buying them with BTC is the cheapest way for now.

On Biswap, each token costs 90 Sats in BTC (BEP20), or less than $0.04. If you wager, it's 8899 Sats each, or $3.50.

So your best bet is to save up, buy some BTC, withdraw through the Binance Smart Chain and exchange them for BFG.